1. Field of the Invention
The present invention relates to filtering of an exhaust stream. The invention also relates to the removal of particulate matter from an exhaust stream. The invention further relates to a wide bore particle trap assembly. The invention still further relates to a method for removing particulate materials from reactor exhaust streams.
2. Background of the Related Art
Nitrides of gallium, indium, and aluminum, and their alloys (III-V nitrides) show much promise in fabrication of a number of light emitting devices. For example, gallium nitride (GaN) is currently used in the manufacture of blue light emitting diodes, semiconductor lasers, and other opto-electronic devices. III-V nitrides may be prepared by techniques including metal organic vapor deposition (MOCVD) and hydride vapor phase deposition (HVPE). A currently preferred method for growth of III-V nitride layers is HVPE. Using gallium nitride as an example, reagent gases for HVPE are ammonia and GaCl. The ammonia is delivered from a standard gas source, while the GaCl is prepared by passing HCl over liquid gallium. Residual, un-reacted HCl or by product HCl, henceforth also referred to a free HCl, also enters the HVPE reactor, and reacts with the ammonia to form ammonium chloride as a byproduct. Ammonium chloride is a white powder that may condense inside the reactor and which can easily block the exhaust line of a HVPE system. If such blockage occurs, the HVPE system must be shut down and epitaxial growth is aborted, leading to decreased productivity, as well as added operating and maintenance costs. Further, such blockage events can lead to catastrophic failure and damage of the reactor tube.
A particle trap is typically used in the HVPE exhaust line to mitigate against blockage of the system. However, due to the relatively large quantities of ammonium chloride involved in carrying out HVPE, prior art particle traps are themselves prone to frequent saturation and blockage. The present invention addresses problems associated with the removal of particulate matter from the exhaust stream of a reactor, such as a HVPE reactor, as will be described fully hereinbelow.